COVER STORY | MARVEL
A MARVEL machine
The MARVEL microreactor is on a fast track to development at INL where it will be the point of the spear on advanced microreactor deployment
LED BY IDAHO NATIONAL LABORATORY (INL), the Microreactor Applications Research Validation and EvaLuation (MARVEL) project is a liquid-metal cooled microreactor with a rated peak capacity of 100 kWth. Based on existing technology and using off-the-shelf components where possible, the philosophy behind the MARVEL test bed is to allow for rapid construction to allow demonstrations of microreactor technology and applications promptly. John Jackson, National Technical Director of the
Department of Energy’s Microreactor Program, explains: “MARVEL is a very small microreactor with the primary goal of developing an operational microreactor as rapidly as possible and with as little cost as possible. That means we don’t make technology choices with economics in mind necessarily, or commercialisation in mind, but rather to get something operational as soon as possible that would demonstrate some of the nuanced characteristics of micro reactors.”
The DOE Microreactor Program works synergistically
with related DOE programs such as the National Reactor Innovation Center with a goal to accelerate the advanced reactor technologies route to market. The Microreactor Program is designed to support R&D related to the development, demonstration, and deployment of very small, factory-fabricated, transportable reactors to provide power and heat for decentralised generation in civilian, industrial, and defence applications.
As Jackson tells NEI: “We loosely characterised its levelised cost of electricity as something like US$1000/ kWh owing primarily to the fact that we’re not doing this to put commercial power on the grid. We’re doing this to demonstrate capability, build processes and procedures in support of what we expect to be a line of commercial demonstrations to be conducted at the Idaho National Laboratory and other locations.” Indeed, the design choices were made to get the reactor up and running sooner rather than later rather than with extensive economic considerations. Design choices for MARVEL include the use of four Stiring engines which are expected to generate a total of around 20 kWe and it will be fueled with high-assay, low-enriched uranium (HALEU) fuel of the TRIGA – Training, Research, Isotopes General Atomics – uranium-zirconium hydride design. Although it is rated at 100 kW, MARVEL will be operated at about 85 kWth. “Stirling engines are more or less off the shelf. We have
to do a little bit of radiation hardening for our use, but it’s expected to be minimal. Sodium potassium, NaK, the primary coolant, we’ve got previous operating experience with the Experimental Breeder Reactor and the fuel itself is a very widely used fuel. We did that on purpose because it’s got a very high negative coefficient of reactivity associated with it, so it’s very safe. It also has been used in licensed reactors and it’s very typically used in university reactors. It’s a self-moderating uranium zirconium hydride with slight modification from the university fuel. The slight modification is mostly geometric. The MARVEL fuel element consists of five fuel meats, whereas a standard TRIGA element consists of three fuel meats,” says Jackson.
Fast track to microreactor deployment With the development goal primarily fast track deployment, operations are expected to begin sometime in the 2025-2026 range. MARVEL itself recently reached a very significant milestone in that it completed its 90% final design at the end of September of 2023. “This is significant because it means that we’re more or less moving from a design phase to an execution phase and we’ve taken a major step toward fabrication and construction,” says Jackson.. The microreactor technology is expected to begin
operation at INL’s Transient Reactor Test Facility, also known as TREAT, within the next two to three years. However, some issues with fabrication have pushed
Above: An illustration showing the MARVEL reactor as deployed Source: DOE 12 | December 2023 |
www.neimagazine.com
operations back from the original scheduled start date. Jackson explains: “We’re working through some issues with fabricators. There are some small ancillary components like parts of the reactivity control system that have been fabricated but we’ve had a few issues within the supply
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